Metal-founding.



crucible.

" 4 s'ra'rns are 1 rare.

CHARLES L. SPINNEY, 0F LYNN, MASSACHUSETTS, ,ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

METAL-FOUNDING'.

11 ,091 542. No Drawing.

To all whom it may concern Be it known that I, CHARLES L. SPINNEY, a citizen of the United States, residing at Lynn, in the county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Metal-Founding, of which the following is a specification.

Certain metals, such as copper and silver, when fused absorb considerable gas such as air, or furnace ases. When the metal solidifies the gas orms blow holes, and reduces the mechanical strength and electricalconductivity of thecast metal.

In accordance with my present invention soundcastings of high electrical conductivity are produced by bringing the molten metal into contact with a comparatively large amount of a flux, such as boric anhydrid, in such a manner that the flux comes into thorough and intimate contact with the molten metal for a prolonged inter val of time just prior to casting.

In the preferred method ,of carrying my invention into effect, about two or more parts of boric anhydrid, B 0 for every 100 parts of metal to be cast, are placed mixed with some inert material, as charcoal, or even coarse clean sand, in the bottom of a The copper, or other metal is placed upon the mixture and is then not only melted but preferably superheated. It should be protected from direct contact with the air by a layer of charcoal. Copper is preferably heated to a temperature of about 1300 C. The charcoal containing the boric anhydrid does not rise above the metal even when the latter is melted, due probably to some surface tension effect as it is not wet by the copper. As the boric anhydrid is thus melted below the copper it may be gradually and thoroughly stirred into the melt to elfect purification. A graphite rod is prefera'bly used for this purpose. The charcoal finally rises to the top when the metal is agitated. The melted boric anhydrid also finally floats on the metal. The metal is cast as quickly as possible after purification to avoid further contamination. When copper is treated in this manner castings having conductivities as high as 90 to 95% Matthleson standard may be obtained. Apparently the gases exist partly as a compound of the metal and partly are merely dissolved. For example, oxygen is present as copper oxid Specification of Letters Patent.

Application filed February 1, 1913.

Patented Mar. 31, 1914.

Serial No. 745,612.

and dissolved oxygen in a state of equilib mum. The boric anhydrid dissolves copper OXlCl and as some is thus removed more is formed until the copper is purified. I do not wish to be limited, however, by this theory. It is also to be understood that fluxes containing boric anhydrid even as a salt, such as borax, may be used instead of the uncombined anhydrid. Therefore, I desire that borate and-boric anhydrid be considered equivalents although the appended claims all specifically call for boric anhydrid. \Vhile I have described In process with special reference to the puri cation of copper preliminary to casting I wish it to be understood that it is of general application to metals absorbing gases in the melted state. I am aware that it has been suggested heretofore, to purify copper with boric anhydrid but to the best of my knowledge heretofore no method has ever been devised of successfully using boric anhydrid to produce cast copper of high conductivity.

What I claim as new and desire to secure by Letters Patent of the United States is 1. The process of preparing copper for casting which consists in bringing the same in a molten state in contact with a mixture of a flux comprising boric anhydrid and an inert material which will retain the anhydrid underneath the melted copper and feeding the anhydrid gradually into the melt and maintaining the same long enough in contact with the copper to effect a purification.

2. The process of obtainin cast metal ofthe copper group of high con uctivity which consists in progressively stirring boric anhydrid into contact with said melted metal beneath the surface of the metal, stirring the melted metal to work the anhydrid gradually to the surface, and casting the metal while'in a purified state.

3. The process of producing cast copper of high conductivity which consists in melting the copper while protected from direct contact with air above a mixture of charcoal and boric anhydrid, progressively working the anhydrid to the surface by stirring,rand then immediately casting the purified copper.

4. The process which consists in melting copper above a mixture of and boric anhydrid, heating the copper to a temperature of about 1-300" C. while the inert material.

and casting the copper.

Q LOELE LQ boric anhydrid is retained beneath the same the metal while the metal is heated to about 10 by the inert material, then progressively 1300 C.

stirring the boric anhydrid into the copper In witness whereof, I have hereunto set my hand this 30th dayof January 1913.

5. The process of purifying copper preparatory to casting which consists in super- 7 CHARLES SPINNEY' posing the melted metal upon about 2% of Witnesses: boric anhydrid mixed with charcoal and JOHN A. McMANUs, Jr.,

gradually working the anhydrid through JAMES E. MINKLER. 

